The overriding objective of the proposed 2 year project is to describe, both quantitatively and qualitatively, the consequences of fertility for child and maternal health status in a population of low socio-economic status whose environment is undergoing very rapid socio-economic change. Achievement of this objective will aid the design of population and health care policies according to the biological, social and cultural needs of their target population groups, and might suggest trends which warrant increasing control. The sample population consists of approximately 200 ever-parous North Thai women and a 1964 birth cohort of their children who are known to the co-investigator from previous research. The sample represents an "emerging urban poor" sector of a Third World country, a population group known to be at high biological and social risk. A control sample from urban high socio-economic status families matches children on year of birth, birth order and number of surviving siblings, and matches sizes of samples with the study samples. Previous research has described the major fertility behaviors and family structure characteristics of the study sample, in addition to obtaining baseline data on child health and growth status. The proposed research will obtain longitudinal data to improve the productive value of the previous cross-sectional findings, and will determine how closely the findings are related to socio-economic status. Measures of fertility include: contraceptive usage, maternal age at childbearing, fetal wastage, infant and child mortality, child-spacing intervals, family size, and birth order. Maternal health-illness status will be measured by anthropometric and laboratory techniques, brief clinical examination by the Investigator, and self-evaluations by informants. Measurements of child health-illness-growth status will repeat observations made in 1972-74, providing a 3 years' longitudinal follow-up of both the study and control child samples. Data will be computer-analyzed and written up at the East-West Population Institute.